A DisplayPort link consists of a main link, an auxiliary channel (AUX CH), and a Hot Plug Detect (HPD) signal line.
The main link is a unidirectional, high-bandwidth and low-latency channel used to transport isochronous data streams such as uncompressed video and audio.
The auxiliary channel is a half-duplex bidirectional channel used for link management and device control. The HPD signal also serves as an interrupt request by the sink device.
The current DisplayPort (DP) standard, available from VESA, (v1.2a) only streams audio and/or video out from a source device (e.g., a graphics processing unit (GPU) and its software) to a sink device (e.g., a local flat panel or an external monitor). In the extended DisplayPort specification (v.1.4), input/output (IO) support is limited to touch information transmitted in the form of processed Human Interface Device (HID) packets that can be transported over the auxiliary (AUX) channel.